A covering device or protective screen for machine tools is known from DE 20 2005 014 233 U1 and has a link apron with a plurality of links connected to one another in an articulated manner and sliding elements arranged on the links at the end. The sliding elements, together with the links, form a guide gap, into which a linearly running guide rail extends. The link apron can be displaced along the guide rail, so a working space of the machine tool can be covered in order to thus prevent dirt or metal chips leaving or entering.